.\"	$OpenBSD: SSL_pending.3,v 1.1 2016/11/05 15:32:20 schwarze Exp $
.\"	OpenSSL a528d4f0 Oct 27 13:40:11 2015 -0400
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.\" Bodo Moeller <bodo@openssl.org>, and Matt Caswell <matt@openssl.org>.
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.Dd $Mdocdate: November 5 2016 $
.Dt SSL_PENDING 3
.Os
.Sh NAME
.Nm SSL_pending
.Nd obtain number of readable bytes buffered in an SSL object
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft int
.Fn SSL_pending "const SSL *ssl"
.Sh DESCRIPTION
Data is received in whole blocks known as records from the peer.
A whole record is processed, for example decrypted, in one go and
is buffered until it is read by the application via a call to
.Xr SSL_read 3 .
.Pp
.Fn SSL_pending
returns the number of bytes which are available inside
.Fa ssl
for immediate read.
.Pp
.Fn SSL_pending
takes into account only bytes from the TLS/SSL record that is
currently being processed (if any).
If the
.Fa ssl->read_ahead
flag is set (see
.Xr SSL_CTX_set_read_ahead 3 ) ,
additional protocol bytes beyond the current record may have been
read containing more TLS/SSL records.
This also applies to DTLS.
These additional bytes will be buffered but will remain unprocessed
until they are needed.
As these bytes are still in an unprocessed state,
.Fn SSL_pending
will ignore them.
Therefore it is possible for no more bytes to be readable from the
underlying BIO (because the library has already read them) and for
.Fn SSL_pending
to return 0, even though readable application data bytes are available
(because the data is in unprocessed buffered records).
.Sh RETURN VALUES
.Fn SSL_pending
returns the number of buffered and processed application data
bytes that are pending and are available for immediate read.
.Sh SEE ALSO
.Xr ssl 3 ,
.Xr SSL_CTX_set_read_ahead 3 ,
.Xr SSL_read 3
.Sh BUGS
Up to OpenSSL 0.9.6,
.Fn SSL_pending
did not check if the record type of pending data is application data.
